1. Field of the Invention
The present invention relates to a method of press-connecting an electric wire with a press-connecting terminal and a press-connecting apparatus used in this press-connecting method.
2. Description of the Related Art
A method of press-connecting an electric wire with a press-connecting terminal as shown in FIGS. 5 and 6 is disclosed in Japanese Patent Unexamined Publication No. Hei. 4-48569. Another method of press-connecting an electric wire with a press-contacting terminal as shown in FIGS. 9 through 11 is disclosed in Japanese Patent Unexamined Publication No. Hei. 7-282943.
As shown in FIGS. 5 and 6, a press-connecting terminal 1 has a terminal portion 3 and a press-connecting portion 5. As shown in FIG. 5, a notched slot 9 is provided in a side plate 7 of the press-connecting portion 5 so that edge portions in opposite sides of the notched slot 9 serve as a pair of press-connecting blades 15 and 15 for cutting a coating portion 13 of a coated electric wire 11.
To press-connect the coated electric wire 11 with the press-connecting terminal 1, as shown in FIG. 6, an end portion of the coated electric wire 11 is pressed against the side plate 7 of the press-connecting portion 5 by a press-connecting jig 17. As a result, the coating portion 13 of the coated electric wire 11 is cut with the pair of press-connecting blades 15 and 15 of the notched slot 9 so that a conductor 19 of the coated electric wire 11 is electrically connected to the notched slot 9. Thus, the coated electric wire 11 is electrically connected to the press-connecting terminal 1.
In the press-connecting method shown in FIGS. 9 through 11, a pair of pressing arms 23 and 23 are provided so that the distance between the pair of pressing arms 23 and 23 is narrowed when a sleeve 21 is moved down as shown in FIGS. 9 and 10. Before a coated electric wire 11 is press-connected with a press-connecting terminal 1, the coated electric wire 11 is squashed with the pair of pressing arms 23 and 23 in the direction of the width of a notched slot 9 as shown in FIG. 10. Then, as shown in FIG. 11, the squashed coated electric wire 11 is pressed against a side plate 7 of the press-connecting terminal 1 by a press-connecting jig 25 so that a coating portion 13 of the coated electric wire 11 is cut with a pair of press-connecting blades 15 and 15 of the notched slot 9 in the same manner as in the aforementioned conventional method. Thus, the coated electric wire 11 is electrically connected to the press-connecting terminal 1.
In the conventional method shown in FIGS. 5 and 6, if the center of the coated electric wire 11 is made displaced even slightly from the center of the notched slot 9 when the coated electric wire 11 having a diameter d is to be press-connected with the press-connecting portion 5 having an inner width h (d=h) as shown in FIG. 7, the coating portion 13 may be however squashed between the press-connecting jig 17 and the press-connecting portion 5 so that the squashed coating portion 13 strongly resists when it is cut with the pair of press-connecting blades 15 and 15 and widens the notched slot 9 in directions of the arrows in FIG. 8.
If the notched slot 9 is widened, the coating portion 13 is cut so insufficiently that the electrical connection between the coated electric wire 11 and the press-connecting terminal 1 fails because of no contact between the conductor 19 and the notched slot 9 or because of shortage of contact load therebetween.
In order to solve this problem, in the conventional method shown in FIGS. 9 through 11, the coated electric wire 11 is squashed in the direction of the width of the notched slot 9 as described above.
After the coated electric wire 11 is press-connected with the press-connecting terminal 1, the notched slot 9 is however widened by elastically restoring force of the coating portion 13 so that the electrical connection between the coated electric wire 11 and the press-connecting terminal 1 fails because of lowering of contact load between the conductor 19 and the notched slot 9.
Taking such circumstances into consideration, an object of the present invention is to provide a method of press-connecting a coated electric wire with a press-connecting terminal, wherein a notched slot of the press-connecting terminal is prevented from being widened so that a coating portion of the coated electric wire is cut thoroughly to thereby keep the electrical connection between the notched slot and a conductor of the coated electric wire surely.
Another object of the present invention is to provide a press-connecting apparatus used in the aforementioned method.
According to a first aspect of the present invention, there is provided a method of press-connecting a coated electric wire with a press-connecting terminal, comprising the step of: pressing an end portion of the coated electric wire into a notched slot provided in a side plate of the press-connecting terminal so as to cut a coating portion of the coated electric wire to thereby make a conductor of the coated electric wire electrically connected to the side plate of the press-connecting terminal, wherein before the coated electric wire is press-connected with the press-connecting terminal, the coating portion of the coated electric wire is heated and softened so that a force necessary for pressing the coated electric wire into the notched slot is reduced to be not larger than a predetermined value.
According to a second aspect of the present invention, there is provided an apparatus for press-connecting a coated electric wire with a press-connecting terminal, comprising: pressing means for pressing an end portion of the coated electric wire into a notched slot provided in a side plate of the press-connecting terminal to thereby cut a coating portion of the coated electric wire to electrically connect a conductor of the coated electric wire to the side plate of the press-connecting terminal; and heating means for heating and softening the coating portion of the coated electric wire so that a force necessary for pressing the coated electric wire into the notched slot is reduced to be not larger than a predetermined value before the coated electric wire is press-connected with the press-connecting terminal.